CNC machine tools are common tools for operating bits to cut work pieces. Each CNC machine tool is equipped with a bit-storing apparatus and a bit-changing apparatus. Bits of various types and sizes are stored in the bit-storing apparatus. The bit-storing apparatus includes a transferring mechanism for transferring sockets each for receiving a bit. Initially, the bit-changing apparatus is used to get a selected one of the bits (the “first bit”) from the bit-storing apparatus and engage the first bit with an axle of the CNC machine tool. If necessary, the bit-changing apparatus is used to replace the first bit with another bit (the “second bit”). To this end, the first bit is disengaged from the axle. Then, the second bit is taken from the bit-storing apparatus and engaged with the axle. Finally, the first bit is stored in the bit-storing apparatus again.
In a chain-type bit-storing apparatus, the transferring mechanism is a chain-sprocket unit including a chain engaged with sprockets. The chain includes links each including a socket. The rotation of the sprockets causes the movement of the chain and, therefore, the movement of the bits. There are various chain-type bit-storing apparatuses. The structures of the chain-type bit-storing apparatuses are complicated and the operation of the chain-type bit-storing apparatuses is inefficient.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.